Morphologic and chemical composition of particulate matter in motorcycle engine exhaust

Abstract

Despite the fact that environmental pollution due to motorcycle exhaust gases reports a great increase, motorcycle production exhibits a great increase through the last years. Countries of Asia and Africa are reported to be the major regions where two-wheeled vehicles are a major transportation mode, with tens of millions of units sold per year. Motorcycle exhaust particles are considered to be the major contributor to environmental pollution due to their airborne dispersion, containing great amount of polycyclic aromatic hydrocarbons (PAHs). This study aims at reporting an objective analysis of the main sources of the ambient air pollution as also particle size distribution and chemical composition analysis of particulate matter originated from the exhausts of two-wheeled vehicles used in the territory of Vladivostok, Russia. Various types of two-wheeled vehicles were examined (motorcycles, ATVs, scooters and wet bikes) using different types of engine and fuel system. Experimental results showed that there was no clear relation to the particle size distribution with the engine displacement of motorcycle and the number of strokes and the fuel system. Instead, there were reported two clear assumptions. The first one is that regarding to the motorcycle brand, a few samples did not exhibit a great percentage of PM₁₀ fraction. The second one is that more modern vehicles, that have a harmful gas afterburning system, are usually the source of an increased percentage of PM₁₀ emitted particles. At last, it should be mentioned that the laser particle size analysis method is capable of determining the particle sizes after their agglomeration whereas the optical morphometry method allows to determine the real particle size of emissions. In conclusion, it can be pointed out that the agglomeration of particles can lead to the reduction in the toxicity of particles emissions originated from two wheeled-vehicles.

Keywords: Chemical composition; EDTA, ethylenediaminetetraacetic acid; EFI, electronic fuel injection system; Environmental toxicology; ICE, internal combustion engines; Motorcycle exhaust gases; PAHs, polycyclic aromatic hydrocarbons; PM, particulate matter; PM10, particles with a diameter between 2,5 and 10 μm; Particle size distribution; Polycyclic aromatic hydrocarbons; VEPs, vehicle emitted particles; VOCs, volatile organic compounds.

Graphical abstract

Fig. 1

Particle size distribution of sample 1 measured with laser light scattering.

Fig. 2

Particle size distribution of sample 1 measured with optical morphometry.

Fig. 3

Efficiency for absorption Qabs (red line) and extinction Qext (blue line) as a function of diameter d of the agglomerated debris particles consisting of amorphous carbon (refractive index m = 2.43 + 0.59i) at green light (0.55 μm).